If you're using calorie counts in your diet plan, you might want to leave a little more buffer space. Researchers have found some notable calorie discrepancies between what's given out on health fact sheets and what independent lab tests discover.

In a study by researchers at the American Diabetic Dietetic Association, a Lean Cuisine package of shrimp and angel-hair pasta listed 220 calories but burned up at 319, while a Wendy's grilled chicken wrap (one of the healthiest foods at Wendy's) promised 260 but loaded in at 344 calories. Some restaurant menu items actually came in under their advertised calorie counts, but that wasn't the norm. Researchers pointed out that restaurant portions obviously vary from customer to customer, and frozen meal makers face stiff penalties for selling underweight packages, so they tend to err on the side of heavier portions.

Earlier this week we shared the healthiest and unhealthiest food at McDonald's with you. Our…
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It's a margin of error—20 percent, by the U.S. Food & Drug Administration's reckoning—to keep in mind if your New Year's diet, or any health plan, requires you to keep better track of how much you're really eating during your day.